1. Field of Invention
This invention relates in general to error correction and error concealment of digital data and in particular error correction and concealment for the wireless transmission of digital audio data.
2. Description of Related Art
In a noisy environment digital audio signals transmitted by means of wireless transmission can become corrupted and produce a noticeable audible noise. When the bit error rate of the audio signals approaches 3.0E-3, the audio signals can become quite distorted by the noise. Both random noise and burst noise can corrupt a wireless transmission and a method is needed to provide a way to remove the noise from the audio signal. This could take the form of error correction, and in cases where the noise errors are too many to correct, a form of hiding or concealing of the noise is needed. When noise errors are hidden, the method used needs to be such that the area of concealment is smoothed so as not to cause distortions that result in audible perturbations.
In U.S. Pat. No. 5,745,582 (Shimpuku et al.) a method and a system is disclosed to transmit and receive a digital audio signal with ECC by means of an optical transmission. In U.S. Pat. No. 5,745,532 (Campana, Jr.) a system and method is disclosed for digital wireless data which uses dual data streams delayed in time from one another to provide replacement data to the stream which has an uncorrectable error. In U.S. Pat. No. 5,742,644 (Campana, Jr.) reconstruction and re-synchronization are done for wireless serial transmissions where fading causes uncorrectable errors beyond the correction capability of ECC. In U.S. Pat. No. 5,673,363 (Jeon et al.) a method for error concealment is described where frequency components, in the last segments of a frame where an error does not occur, are used to reconstruct the frequency components of subsequent frames that are in error. In U.S. Pat. No. 5,412,638 (Koulopoulos et al.) an error correcting scheme for a digitized audio output of a CD player is described using a finite impulse response filter.
The wireless transmission of digital audio data exposes the data to corruption by noise that is random and noise that occurs in bursts. When bit error rates of the transmitted data are low (&lt;&lt;3.0E-3), the need for error correction ranges from not being needed to being satisfied by well known error correction techniques. However, as the bit error rate approaches 1.0E-3 to 3.0E-3 or higher, more of the transmitted digital audio data will be found to be corrupted and will require means for concealment of the corrupted data that exceeds the limit of the capability of ECC (error correction code).